The way we identify paper here in the USA frustrates many people. Most of the world utilizes the metric system but here in the US, we use a nomenclature related to the manufacturing process. After reading this article you'll be able to differentiate paper by types, thickness, weight, application, finishing and use. You will be able to compare how paper in USA is identified elsewhere.
You will be able to answer questions such as "How is a 20# (pound) copy bond paper different from a 60# offset paper?"
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All About Paper Weights: Understand "Basis Weight", Bond, Book Grades, Text Grades, Cover Stock, Index and Tag.
("U.S. Basis Weight") is defined as the weight of 500 sheets of paper in its basic production size (parent size), before any cuts take place. Find the Chart of Paper Manufacturing Sizes on this same page.
- Example #1: Basis Weight of Bond Paper: A sheet of bond paper comes out of a production line and measures 17x22 inches. If the weight of 500 of those sheets is 20lbs, that bond paper will be identified and labeled as “20lbs”, or “20# bond”. When you cut the 17”x22” sheet into two, you will get 2 sheets each measuring 8.5”x11” which happens to be a “letter size”. Assuming that we have those 500 uncut sheets, we’ll end up with 1,000 sheets of 20# bond paper. Each group of 500 sheets then weighs 10 lbs. Conclusion: The Basis Weight of Bond paper is 20lbs.
If the same components to the paper and thickness were produced out of a sheet of paper that measures 25 x 38 inches, 500 sheets of that paper would weigh 50 lbs. It would be 50lbs basis. So as you can see, the paper, physically, would be the same. But its name would be 50 lbs. instead of 20 lbs. The number itself is not indicative of how thick one paper is when compared to another one.
- Example #2 for 100 lbs coated paper: We will find out the basis weight of a coated sheet of paper.
Here is an illustration that helps visualize this. Coated paper is manufactured in sheets of 25 x 38 inches. In this case, 500 of those sheets weigh 100 lbs. Therefore the Basis Weight for this paper is 100 lbs, also known as 100# coated text paper.
Chart of Paper Manufacturing Sizes to determine Basis Weight Parent Sizes
|Paper Type||Manufacturing Ream Size (Parent Size) inches||Manufacturing Ream Size (Parent Size) ISO - mm|
|Bond (Copy Paper, Ledger, Manifold)||17" x 22"||432 mm x 559mm|
|Book or Text(Coated Gloss or Coated Dull or Offset Paper)||25" x 38"||635mm x 965mm|
|Bristol||22 1/2" x 28 1/2"||571mm x 724mm|
|Cover (Glossy cover stock or uncoated cover stock)||20" x 26"||508mm x 660mm|
25 1/2" x 30 1/2"
|648mm x 775mm|
|Newsprint (Tag)||24" x 36"||610mm x 914.4mm|
Paper is Manufactured at Paper Mills Using Different Machines With Different Technologies.
There are several stages in the manufacturing process with 'finishing' being the last one. Wood chips get transformed into pulp, rollers calender the paper and determine the thickness of the paper. During the production and finishing processes the softness is determined. For glossy or satin paper, a coating gets added to complete the process. Therefore different machines in different widths produce different types of paper.
The end product at the mill is a roll that gets trimmed into flat sheets comprising what is known as the parent size.
Names and Sizes of Paper in the US Standard System
The way to obtain different sizes of paper is by cutting the parent size into fractions. The typical way is to cut the mother sheet in half.
U.S. Standard Paper Sizes
|Ledger||279 x 432||11 x 17|
|Legal|| ||8.5 x 14|
|Letter||216 x 279||9.5 x 11|
|Monarch|| ||7.25 x 10.5|
|Executive||140 x 216||5.5 x 8.5|
|Statement||108 x 140||4.25 x 5.5|
|Business Card|| ||2 x 3.5|
The U.S. Standard System changes the proportions of the sheet of paper once it is cut in half making it difficult to size up or down. The International Systems for paper weight and sizes is designed so that cutting paper in half still keeps the same proportions. That system is known as ISO "A"
The Grades of Paper are defined in terms of its use. Each grade serves a purpose:
- Opaques and Offset Papers
- Coated Papers
- Writing Papers (a.k.a. Correspondence Papers or Bond Papers)
- Text and Cover papers
Opaques and Offset uncoated papers: These are similar with some specific differences
Offset uncoated papers are commodity papers available in large volumes.
Along the years a change in formulations made it alkaline as opposed to acidic, which gives it better archival properties.
Their internal bonding is good, with high surface strength and dimensional stability.
Offset Paper: Typical basis weight for this paper are 50lbs, 60lbs, 70lbs, 80lbs
The finishes of offset papers are
- Vellum finish which is extremely rough
- Patterns: as in Laid and Linen finishes
Opaque Paper:Typical basis weight for this paper are 50 lbs, 60lbs, 70lbs, 80lbs
The quality of pulp use is better so it has higher opacity than offset paper (which means less see-through) It is more expensive than the offset grade. The finishes of opaque papers could include a very light clay layer giving it a very high quality.
Coated Papers have 5 types of finishing and 5 qualities
Coated papers are made like offset papers but have a clay coating added on their surface before calendering. The coating creates a gloss or sheen on the paper's surface. This coating holds ink better and helps get a smaller dot that in turn produces a better printing quality. The clay often accounts for as much as half of the weight of the paper. Therefore the quality of the clay determines how bright, printable and strong the paper will be (resistance to tear, shear, etc)
The calendering process produces the following types of finishes
- Cast Coated, which are very shiny
The quality is determined by the brightness, smoothness, mechanical properties (resistance, shear, etc) and stability of thickness among others. Paper is rated from 1 to 5, 1 is the highest quality. 5 is the lowest quality
Writing Paper also known as Correspondence Papers or Bond Papers
This writing grade historically called Bond papers are designed for letterhead, corporate identity and home or office printers. They perform well for handwriting. These can be done with a watermark or can have cotton fiber to provide an elegant feel and mechanical strength.
Text and Cover papers
These are premium uncoated papers that are available in amazing colors and finishes. Some text papers are lighter while Cover papers are thick and nice for covers, brochures and business cares.
Basis weight that are equivalent
|US Basis Weights||Caliper||Metric|
|Bond||Text||Cover||Index||1 Point = 0.001"||GSM (g/m2)|
|20||50|| || || ||75|
|24||60|| || || ||90|
|28||70|| || || ||105|
|32||80|| || || ||120|
|36||90||50|| || ||136|
|54|| ||74||110|| ||199|
| || ||90||135|| ||245|
| || ||93||140||12.0||253|
| || ||100||150|| ||271|
| || ||130||200||16.0||350|